When we change addresses, we usually get cardboard boxes to pack our belongings. When we paint a wall, we also cover the floor with open cardboard to prevent the paint from spilling onto the floor. But what if this material had other uses? A technology developed at Unicamp with a patent deposit made by the Inova Unicamp Innovation Agency opened up new possibilities and introduced the use of cardboard for construction.
The research was developed with support from the São Paulo State Research Support Foundation (Fapesp) by civil engineer and master's student at the Faculty of Technology (FT) at Unicamp Nathália Schimidt Dias, with guidance from professor Gerusa de Cássia Salado, a specialist in the field. of construction technology. “This cardboard structure that we developed can be used to build a residence, a school, a hospital, a commercial establishment”, said Gerusa.
The invention is a device that connects cardboard tubes vertically and horizontally to form a cage-like structure. On the external and internal side of this structure, sealing panels are placed to close the walls, which can be made of plasterboard or cement. “You make a structure that looks like a bird cage. Instead of using steel, we make the system with cardboard tubes that are prepared from our invention to fix the fence panels”, explains the teacher.
The choice for cardboard was due to environmental reasons. The researchers argue that the tubes be made from discarded paper. “Our idea is to take a material that comes from recycling to reduce the volume of waste in landfills, because it doesn't make sense to cut down a tree to make premium paper, since one of the materials we discard the most is paper. And as the cardboard would be made from discarded paper, if one day there is a demolition, the construction remains can also be recycled and form new products”, explained Gerusa.
In addition to sustainability, everything was designed so that, in the future, structures could be prefabricated, creating practicality and making construction cheaper, which would be faster, as workers would only need to connect the pieces, like playing blocks. to assemble. Another advantage brought by the system is that, as the cardboard tubes are hollow, it is possible to pass all electrical and hydraulic installations through them, without the need for them to be exposed.
Inspiration and breakthroughs
The researchers say that the inspiration for using cardboard tubes came from the Japanese architect Shigeru Ban, who uses the material in his construction systems and has been studied by Gerusa for many years. However, unlike the architect, who prefers to build by hand, the duo sought the path of industrialization. “Shigeru Ban is a Japanese architect and, just like his culture, he does everything very artisanally. We, Westerners, already like large scale, industrialization”, commented the professor.
Furthermore, during her research, Nathália also observed that the architect varied the connections and materials for connectors depending on the construction. “We ended up noticing that, for each construction, he used a different method and material, such as wood, steel or strips of fabric. So we saw that there was the possibility of developing a system that was easier, both from the point of view of technology production and from the point of view of assembly”, explained Nathália.
Thus, according to Nathália, the distinguishing feature of her invention was precisely the connection device, which can adapt to practically all project situations. “The device serves to connect all parts, at all points of the construction process. You have a single piece, which can also be industrially manufactured on a large scale, which solves the entire project, connecting all the cardboard tubes and serving as a point for fixing the panels. The connector also serves to anchor the construction in the ground, creating the base, and to secure the roof”, explained the researcher.
The connector developed for this construction system has great potential for industrial and large-scale production, and it is ideal for manufacturing to be carried out using metal alloys or high-density polymers. “This would speed up manufacturing, which could be done using 3D printers, enabling practical, fast, light, cheap and clean construction,” said Gerusa.
For the development and design of the construction system with cardboard tubes, 3D modeling software was used, such as AutoCAD and 3DS Max. As next steps, the researchers aim to build a test cell. “A partnership for this testing would be very welcome. A next and final step to certify, in practice, the efficiency of the construction system”, commented the teacher.
Resistance and durability
Cardboard, despite appearing to be a fragile material, if sized in tubular form, has a resistance equivalent to that of a tree trunk. “The cylindrical cardboard tube is like a remodeling of the tree trunk. By sizing its variables, the external diameter, the wall thickness and the height, we were able to obtain the resistance necessary to make the pillars of the buildings”, stated Gerusa.
This resistance was proven in laboratory tests, which guaranteed that the construction resists the main stresses and common impacts, in addition to the installation of the frames. Furthermore, the construction system also supports furniture elements such as cabinets and shelves. “The construction must be self-sustaining and resistant to sporadic shocks, such as a person tripping and bumping into a wall”, he explained. However, the researchers add that the tests were only carried out for single-story buildings. For projects with multiple floors, such as a building, new studies are necessary.
Gerusa and Nathália also explain that, as cardboard is derived from cellulose, it requires some protection against humidity. “For cardboard tubes to be highly durable, they must be elevated from the ground, to avoid absorption of moisture by the base, and they must be waterproofed to resist humidity, as even when covered by vertical sealing panels, it is necessary to ensure that the tubes of the structure are not affected by water in cases of possible leaks from the hydraulic-sanitary system”, said the researchers.
Applications and technology transfer
Among the applications of the new construction system, field hospitals, itinerant schools and shelters for construction workers or families left homeless after disasters, such as floods and landslides, stand out. The construction system of cardboard tubes with the connector is part of Unicamp's Technology Portfolio and is available for licensing.
Companies and public or private institutions can license intellectual property developed at the university. This contact is made directly with Inova Unicamp. In addition to access to cutting-edge technologies and the possibility of research in partnership with the university, technology transfer reduces risks associated with the development of new innovative products and processes.
Article originally published on the Inova Unicamp website.
